Adaptive filter and echo canceller

Abstract

An adaptive filter in the form of an FIR or IIR filter performs an adaptive filtering process relative to an input signal using a plurality of tap coefficients. The adaptive filter derives a vector formed by absolute values of the plurality of tap coefficients and weights step sizes of the plurality of tap coefficients using the first vector. The adaptive filter updates the plurality of tap coefficients based on the weighted step sizes. With this arrangement, the optimum tap coefficients can be achieved with high convergence speed. The adaptive filter is applicable to an echo canceller, such as, an acoustic echo canceller or a line echo canceller, so that echo canceling is effectively achieved by updating the tap coefficients with high accuracy and with high speed.

What is claimed is: 
     
       1. An adaptive filter in the form of one of an FIR filter and an IIR filter for performing an adaptive filtering process relative to an input signal using a plurality of tap coefficients, said adaptive filter comprising: tap coefficient updating means including:   means for deriving a first vector formed by current absolute values of said plurality of tap coefficients; and   means for weighting step sizes of said plurality of tap coefficients using said first vector and for deriving a plurality of new tap coefficients based on the weighted step sizes.   
     
     
       2. The adaptive filter according to claim 1, wherein said tap coefficient updating means multiplies said first vector by a given constant which determines an updating rate of said step sizes, said tap coefficient updating means weighting said step sizes based on a result of said multiplication. 
     
     
       3. The adaptive filter according to claim 2, wherein said tap coefficient updating means adds a second vector to the result of said multiplication, said second vector determining initial weighting of said step sizes at the start of operation, and wherein said tap coefficient updating means weights said step sizes based on a result of said addition. 
     
     
       4. The adaptive filter according to claim 1, wherein said tap coefficient updating means adds a second vector to said first vector, said second vector determining initial weighting of said step sizes at the start of operation, and wherein said tap coefficient updating means weights said step sizes based on a result of said addition. 
     
     
       5. An echo canceller comprising: an adaptive filter in the form of one of an FIR filter and an IIR filter for performing an adaptive filtering process relative to an input signal using a plurality of tap coefficients, said adaptive filter estimating an echo caused due to one of signal transmission and signal reception so as to output an echo replica signal: and   removing means for removing said echo replica signal from said input signal so as to output a remainder signal,   wherein said adaptive filter derives a first vector formed by current absolute values of said plurality of tap coefficients and weights step sizes of said plurality of tap coefficients using said first vector, and   wherein said adaptive filter updates said plurality of tap coefficients using said remainder signal and said step sizes weighted so as to correct said echo replica signal.   
     
     
       6. The echo canceller according to claim 5, wherein said adaptive filter multiplies said first vector by a given constant which determines an updating rate of said step sizes, and wherein said adaptive filter weights said step sizes based on a result of said multiplication. 
     
     
       7. The echo canceller according to claim 6, wherein said adaptive filter adds a second vector to the result of said multiplication, said second vector determining initial weighting of said step sizes at the start of operation, and wherein said adaptive filter weights said step sizes based on a result of said addition. 
     
     
       8. The echo canceller according to claim 5, wherein said adaptive filter adds a second vector to said first vector, said second vector determining initial weighting of said step sizes at the start of operation, and wherein said adaptive filter weights said step sizes based on a result of said addition. 
     
     
       9. An adaptive filter, comprising: means for adaptively filtering an input signal using a plurality of tap coefficients;   tap coefficient updating means that repeatedly updates m+1 current tap coefficients h j  (n), j=0 to m, to m+1 updated tap coefficients h j  (n+1), j=0 to m, where n is an integer designating an n-th update, including: means for deriving a first vector A=|h j  (n)|j=0 to m, formed by absolute values |h j  (n)| of the m+1 current tap coefficients, and   means for weighting step sizes of the plurality of tap coefficients using the first vector A and for deriving the m+1 new tap coefficients h j  (n+1), j=1 to m, based on the weighted step sizes.     
     
     
       10. An adaptive filter according to claim 9, wherein said weighting and deriving means include: means for generating a step size vector α(n) by multiplying the first vector A by a scalar constant β and adding thereto a vector p that represents an initial value of a step size vector α(n) which is vector α(0); and   means for generating a vector h (n+1) according to the following equation:   vector h(n+1)=vector h(n)+e(n)•vector α.sup.T (n)•vector x(n)/∥vector x(n)∥.sup.2,     wherein vector h(n) includes as vector elements the tap coefficients h j  (n+1), j=0 to m, e(n) is an echo remainder signal and vector x(n) is a received signal vector.